Flavors from Lipids

Surfactants can act like lipids or emulsifiers in solubilizing flavor materials in surfactant micelles. Headspace analysis techniques were used to follow the release of several common dentifrice flavorants from a solution containing the surfactant sodium lauryl sulfate. Water/micelle partition coefficients were derived to describe the solubilization of the flavorants in tiie surfactant micelle (76). Initially, the flavor is solubilized in the surfactant micelle. As both the micelle and flavor concentration decrease on dilution, flavor compounds, which are highly soluble in the micelle, preferentially increase in the headspace [HGURE11]. 

The major cause of deterioration of food products is lipid oxidation, from which low-molecular-weight, off-flavor compounds are formed. This deterioration is often caused by the oxidation of the unsaturated lipids present in foods. Off-flavor compounds are created when the hydroperoxides, formed during the initial oxidation, are degraded into secondary reaction compounds. Free radicals are also formed which can participate in reactions with secondary products and with proteins. Interactions with the latter can result in carbonyl amino... 

Since 1980, there has been rapid development of SFE, for the extraction of fossil fuel and environmental samples such as pesticides, hydrocarbons, phenolics [12,13], food products including hops, fats and lipids from butter, perfumes and flavors from natural products [14], and oligomeric materials or additives from polymers [IS]. 

In initial work, L- a-phosphatidylcholine (lecithin) from egg yolk was selected as the phospholipid, and later studies compared other phospholipids and lipid extracts from meat. As the study originated from investigations of cooked meat flavor, the model system reactions were carried out in aqueous solution buffered with phosphate at an initial pH of 5.7 and concentrations of the reactants were selected to approximate their relative compositions in mammalian muscle. The reactions were carried out under pressure... 

A. Amoldi and G. Boschin, Flavors from the reaction of lysine and cysteine with glucose in the presence of lipids, in Thermally Generated Flavors Maillard, Microwave, and Extrusion Processes, T. H. Parliment, M. J. Morello, and R. J. McGorrin (eds), American Chemical Society, Washington, DC, 1994, 240-250. 

Natural food flavors such as terpenes, hydrocarbons, alcohols, aldehydes, ketones, esters, acids, lactones, amines, sulfur compounds are enzymatically produced in fruits and vegetables. On the contrary, processed food develops its characteristic acceptable flavors from chemical reactions within its components at temperatures far below those at which its major components, i.e., lipids, proteins and carbohydrates pyrolyze. 

Sensory evaluation of lipid oxidation has been conducted by many researchers (98-100). However, as a subjective method, the reproducibility of sensory analysis is generally considered worse than that of chemical or instrumental methods. More recently, use of an electronic nose to monitor the formation of volatile compounds associated with off-flavors from hpid oxidation has been proposed to supplement information from human sensory panels (101). 

Haymon, L.W., J.C. Acton, Flavors from lipids by microbial action, in Lipids as a Source of Flavor, M.K. Supran, Ed., Amer. Chem. Soc., Washington, D.C., 1978, p.94. 

If one considers the factors that influence rate of LO, one can see that very dry products high in polyunsaturated fatty acids are most likely to develop off-flavors due to LO. However, one must also recognize that virtually all foods contain sufficient lipid to develop off-flavors via LO. It is only a question of whether some other mode of product failure occurs before LO becomes significant. It is a question of time. It was thought that low-fat (or no fat) foods would be less likely to suffer from LO. However, it has been found that these products are actually more susceptible to off-flavors from LO than the full fat versions of these products since fat tends to mask off-flavors. Reducing the fat content reduces any masking, making off-flavors more visible to the consumer. 

A review by Bailey and Swain ( ) cited several references which indicated nitrite was responsible for cured meat flavor. These same authors presented chromatograms of volatiles from cured and uncured hams and while the chromatograms were similar, some quantitative differences led to the conclusion that the major difference due to nitrite was its reactivity to retard lipid oxidation. Greene and Price ( ) suggested, however, that sodium chloride was the major factor responsible for cured meat flavor rather than sodium nitrite or an absence of lipid oxidation. It has been concluded from other recent work (2) that nitrite was necessary to produce a typical ham aroma and flavor as well as to retard the development of off-odors and flavors during storage of cooked cured meat. 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Human perception of flavor occurs from the combined sensory responses elicited by the proteins, lipids, carbohydrates, and Maillard reaction products in the food. Proteins Chapters 6, 10, 11, 12) and their constituents and sugars Chapter 12) are the primary effects of taste, whereas the lipids Chapters 5, 9) and Maillard products Chapter 4) effect primarily the sense of smell (olfaction). Therefore, when studying a particular food or when designing a new food, it is important to understand the structure-activity relationship of all the variables in the food. To this end, several powerful multivariate statistical techniques have been developed such as factor analysis Chapter 6) and partial least squares regression analysis Chapter 7), to relate a set of independent or "causative" variables to a set of dependent or "effect" variables. Statistical results obtained via these methods are valuable, since they will permit the food... 

The lipid components of food are known to be critical in the development of much of a food s flavor. Modifications to lipid modifying enzymes such as lipases have led to new products useful in the rapid preparation of other food components Chapter 13,14), Better utilization of lipid constituents in food products can be gained from a better understanding of the thermodynamic and physicochemical characteristics of emulsions. Significant advancement in emulsion chemistry and food engineering have recently appeared in the literature and are an important portion of this volume Chapter 19),... 

Standards and Controls. In all experiments, the 85 g standard patties were made from freshly ground top round steaks (excess fat trimmed) and immediately frozen in covered glass petri plates until the day of the assay. The fat content was routinely from 4-5%, determined by the method of Koniecko (57). The standards generally had relatively low values for hexanal, total volatiles (TV) and TEARS, and low intensity values for painty (PTY), cardboardy (CED), sour (SUR) and bitter (ETR). These results indicated the absence of lipid oxidation and no formation of off-flavors. As expected, the desirable flavor notes, cooked beef/brothy (CEE), beefy/meaty (EM), brothy (ERO), browned/caramel (ERC) and sweet (SWT) had high intensity values. 

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